Kmcoldcars

I have a 1991 Corvette 6 speed with a Procharger supercharger. It has been running fine until recently.
I took it out for a drive one morning and it started missing a lot. I went about 1 block downhill, stopped for the stop sign and started out. That is when it started missing. I immediately turned around and nursed it into the garage. There were no codes.
A few days later I started it up just fine. It idled well, so I ran it up the hill near my house, about 2 blocks. On the first run up the hill it missed a little bit when under load. The next 2 runs up the hill were fine, so Dan and I took it for a ride. After about 2 miles it started missing a bit and kept getting worse. It then died. I tried restarting it and it would crank fine but would not start. I coasted backwards and got it off the road. After sitting for a while it would start and immediately die. If I tried to start it again it would crank but not start. If I waited a few minutes it would start and die after about 1 second.
The tow truck took it home.
The next day I started it just fine. The fuel pressure gauge said 38 pounds of pressure while idling. I turned the car off and the pressure held for 10 minutes with no problem. I started the car again and it idled fine. Then it just died, there was a clicking sound from the front of the car, and the service engine light was flashing on and off. Then all of that stopped. There were no codes.
I restarted the car with no problem. It idled OK for a while, then the idle dropped to about 400, then went up to about 1500, then back to its normal 800. Then the car died again. I tried to restart it and it ran for about 1 second and then died. I immediately tried to restart and it cranked fine but did not start. I let it set for a few minutes and it started just fine, then died after about 1 second. At all times the fuel pressure gauge said 38 pounds of pressure. The battery voltage after all this, with the ignition off, measured 12.35 volts.
The vacuum gauge shows a steady 21 inches of vacuum while the car is idling.
The car has an aftermarket MSD ignition system.
Any ideas?

lectroglide

I was their with keith and what was weird was after the car was turned off you could hear a clicking noise in the motor compartment like the car was possed and wanted to start on its own, then it stopped..........Come on guys we need atleast one input to get some ideas goin, all comments welcome

antfarmer2

Should be dark in a bit open the hood and have someone crank it and look for sparks and archs. hope it's not your opti going

Paul Workman

For one, I'd want to do a scan with it running.

That said, the fuel pressure for a 91 L98 car (listed in my Corvette Fuel Injection reference indicates 14-47 psi, w/ the engine OFF, and should hold that within a pound or two for 30 minutes; against a possible leaking injector(s).

And too, looking for clues, I'd be curious what the fuel pressure was when the engine was running.

"After it warms up..." is a classic description of an electrical fault too. And, say for instance, if the coil were going bad, it could well demonstrate symptoms similar to yours, AND not leave any tell-tale codes either.

That's why I suggest a scanning. A scanner is the best investment in tools I ever made for these cars!

Fuel - air - spark @ the right times is always required. Yours is missing something!

ovrebo1

Sounds a lot like a fuel pump problem I've had on several of my trucks that were heavily modded. The hose between my in tank pump and the metal pickup tube would become split, but before I knew that was the issue, it had a lot of the same issues you described.

I would inspect every inch of fuel line and and rubber in the system. If you had a pump you could temporarily swap in that would be helpful too

lectroglide

thanx but that doesn't explain the electrical shorting out symptom

ovrebo1

Aren't a lot of GM's notorious for bad FP grounds?

C409

....... I would look at the coil , the Ignition Control Module in the distributor , and the fuel supply (pressure) when it starts to act up .....

kg4fku

I had a similar issue with a Mustang GT (1994). Car would run great until warmed up. Once warm it would then would miss and die. Long story short it was the ignition control module. Took forever to figure it out though. The module would test fine when we took it in to the local shop as it would be cooled down by then. There was a thermal separation of an electrical connection inside the module. Of course the module was sealed in epoxy so we were unable to actually see the failure.

Kmcoldcars

Thank you for all the responses.
A 1991 does not have an optispark.
The fuel pressure stayed at 38 pounds while it was running, when it died, and when it would not restart. It stayed greater than 36 pounds for at least 15 minutes after the engine was shut off, so I do not think it is a fuel problem.
I would tend to think it is an electrical problem. The car has an MSD ignition system, which I know nothing about, as it was on there when I bought it.
I will be out of town for about 10 days and will start back on it then. I will let you know what I find and will be asking for help. Most likely I will get a new ignition control module, if they are not outrageously expensive, and see if that makes any difference.

antfarmer2

Sorry my bad on the opti missed the year. With the icm make sure you use the heat sink grease and I would check the ground on it first have heard of problems with bad grounds on it.. If it does not start when hot could be the coil.

86C4Z51

Without hooking it up to a diagnostic, the ECM sounds like a good place to start.

Teothe1nonly

I just went through this too, in my case it ended up being the Injectors. Some of the injectors got plugged up and was getting enough fuel. I checked pressure with a Fuel pressure gauge and everything was right on the money, I couldn't understand it anymore so I pulled the fuel rail, turned the key with the help of a friend, and lone behold 3 or 4 injectors werent working. When you give it gas, the other injectors compensate and try to start the car...foot off gas, the working injectors can't get enough fuel in due to others being bad. GOOD luck


Reguards,
-T

lectroglide

turned out to be a bad ECM

86C4Z51

I'll be darned. Internet troubleshooting.